Ana María Gennaro

Detergent resistant domains in erythrocyte membranes survive after cell cholesterol depletion: an EPR spin label study.

We use electron paramagnetic resonance (EPR) with liposoluble spin labels in order to study the lipid structures obtained after Triton X-100 extraction of erythrocyte membranes. The apparent order profile in these detergent resistant membranes (DRM) is very similar to that of the parent membrane, although with higher absolute values, consistent with a liquid-ordered state. DRM could also be obtained from erythrocytes previously depleted in a 40% of their membrane cholesterol, in apparent opposition to the phenomenon of raft disruption reported by other authors. However, the protein profile of these samples showed important differences with that of DRM from untreated cells. The analysis of our results suggests that the effect of Triton X-100 on cholesterol depleted erythrocytes is limited to the solubilization of raft proteins, without disrupting the lipid matrix of DRM.

Lysophosphatidylcholine-arbutin complexes form bilayer-like structures.

Arbutin is known to suppress melanin production in murine B16 melanoma cells and inhibit phospholipase action. This encourages the possibility to stabilize it in lipid aggregates for its administration in medical applications. Thus, it was of interest to demonstrate that monomyristoylphosphatidylcholine (14:0 lysoPC) and arbutin may form association complexes. This was studied by Electron Microscopy (EM), 31P Nuclear Magnetic Resonance (31P NMR), Electronic Paramagnetic Resonance (EPR) and Fourier Transform Infrared Spectroscopy (FTIR). EM images show the formation of particles of c.a. 6 nm in diameter. For a 1:1 lysoPC-arbutin molar ratio 31P NMR shows a spectrum with a shoulder that resembles the axially symmetric spectrum characteristic of vesicles. The addition of La3+ ions to the arbutin-lysoPC complex allows one to distinguish two phosphorous populations. These results suggest that arbutin-lysoPC forms vesicles with bilayers stabilized in an interdigitated array. FTIR spectroscopy shows that arbutin interacts with the hydrated population of the carbonyl groups and with the phosphates through the formation of hydrogen bonds. It is interpreted that hydrophobic interactions among the phenol group of arbutin and the acyl chain of lysoPC are responsible for the decrease in acyl chain mobility observed at the 5th C level by EPR. A model proposing the formation of interdigitated bilayers of arbutin-lysoPC could explain the experimental results.

Bioactive compounds delivery using nanotechnology: design and applications in dairy food

The novel properties of nanomaterials offer many new opportunities for the food industry. Different types of nanostructures can be incorporated into food in order to introduce new functionalities. These include; nanoliposomes, nanoemulsions, and nanoparticles. The sizes, shape, and internal structure of the particles vary considerably depending on the method and materials used to fabricate them. Bioactive compounds such as vitamins, antioxidants, and lipids can be protected using nanotechnology, even enhancing bioactivity and functionality. The design and application of nanoderived assemblies as tools for improved delivery and bioavailability of bioactive nutrients is promising. In this sense, success depends on scientific knowledge about degradation mechanisms of nutrients and major factors affecting them. Besides, it is necessary to review information in order to decide which delivery system fix with the desired application. In particular, nanotechnology has the potential to revolutionize dairy technology in the coming years.